autologin: Don't use `count()' for is empty checks

Using `count()' in favor of `empty()' for empty checks on arrays is bad habit.
While there's literally no performance gain in the "fixed" scenario, there's one on large arrays
and thus should be avoided everywhere.

refs #6462

library/Icinga/User.php

@@ -446,7 +446,7 @@ class User
      */
     public function isRemoteUser()
     {
-        return (count($this->remoteUserInformation)) ? true : false;
+        return ! empty($this->remoteUserInformation);
     }
 
     /**